Application of harmonic included CPL‐QPHD model of GaN device for broadband PA design

Abstract

In this work, a harmonic included canonical piecewise linear (CPL) function based quadratic poly-harmonic distortion (QPHD) model is presented. The proposed model employs the framework of the standard QPHD model, making use of the CPL functions for interpolation of the amplitude of the dominant input signal. Compared with the standard QPHD model, the model described in this work is able to predict transistor behavior at different levels of input powers with one single set of model coefficients. The harmonic information has also been added in this model to make it more complete. The model is validated in terms of both DC and RF behavior through simulated data of a 10 W gallium nitride (GaN) high-electron-mobility transistor (HEMT) over a wide range of load conditions and power levels. In addition, the model is implemented in advanced design system (ADS) with frequency-defined device (FDD), and applied for a broadband power amplifier (PA) design. Chebyshev low-pass topology is used for both input and output matching network design. Finally, a broadband PA is implemented with an average power added efficiency of 66.23%, an average power of 41.09 dBm, and an average gain of 13.09 dB across the operating frequency range from 0.6 to 1.7 GHz. The simulation results of the harmonic included CPL-QPHD model are highly matched with the measurement results of the designed PA, demonstrating the feasibility of applying the proposed model for broadband PA design.